This research is amied at characterizing the regulation of normal steady state granulocyte production; the cellular mechanisms by which granulocyte production can be moderated and the humoral and cellular feedback loops responsible for the modulation. Granulopoiesis is studied in vivo in the dog and in in vivo and in vitro culture systems using standard in vitro agar culture, diffusion chamber culture, plasma clot diffusion chamber culture. Stem cells are separated by adherence, velocity sedimentation and immunoflorescent cell sorting in a fast flow system.